MUTUAL ANTAGONISM OF INORGANIC SALTS 323 



impermeable to water, but that in a physiologically unbalanced salt 

 solution this natural impermeability is lost, and hence, if the solution 

 is at the same time hypertonic, water diffuses out of the egg and the 

 resultant increase in specific gravity causes it to sink. The same solu- 

 tions which cause this loss of water are also toxic for the developing 

 embryos. Hence the toxicity of unbalanced solutions is associated 

 with an increased permeability of the cells. 



The same conclusion has been reached by Osterhout in quite another 

 way. This observer has employed the electrical conductivity of plant- 

 tissues as a measure of their permeability for ions, that is of the resist- 

 ance which the surfaces of the cells offer to the transport of ions across 

 them. Discs about 13 m.m. in diameter were cut from the fronds of 

 marine'algse (Laminaria), the average thickness of a frond being about 

 0.5 m.m. One or two hundred of these discs were then packed together 

 like a roll of coins, into a solid cylinder of from 50 m.m. to 100 m.m. 

 in length. They were held in place by glass rods so arranged as to make 

 a hollow cylinder which closely fitted over the outside of the solid cyl- 

 inder of tissue. The spaces between the rods allowed free access of 

 various salt solutions to the living tissue. At each end of the cylinder 

 of tissue was placed a platinum electrode which could be pressed 

 firmly by means of a screw against the opposite ends of the cylinder. 

 The conductivity of the cylinder was estimated in the usual way. The 

 surface in and out of which ions were forced by the current, amounted 

 to from 26,000 to 53,000 square centimeters; an increase in the con- 

 ductivity of the cylinder implied decreased resistance to the passage 

 of ions across the surfaces of the tissue, i. e., an increased permeability 

 for electrolytes, while a decrease in the conductivity of the cylinder 

 implied, on the contrary, decreased permeability of the cells. It will 

 be observed that the permeability measured by Osterhout was per- 

 meability for dissolved electrolytes, while that measured by Loeb was 

 permeability for water. 



On transferring the cylinder of Laminaria from sea-water to Sodium 

 Chloride solution of the same temperature and conductivity (0.52 

 molecular), the resistance fell from the initial value of 1100 ohms in 

 sea-water to 890 ohms in ten minutes. In fifteen minutes it had fallen 

 to 780 ohms, after sixty minutes to 420 ohms, and thereafter continued 

 to fall steadily until it reached a constant minimal value of 320 ohms, 

 which was found to be the resistance of a column of sea-water of the 

 same length and diameter. In other words, in pure sodium chloride 

 solution the cell-surfaces in Laminaria increase in permeability until 

 finally they interpose no resistance at all to the transference of ions 

 across them. 



A very striking contrast to this result is obtained if a similar column 

 of tissue be transferred from sea-water to a solution of Calcium Chloride 

 having the same conductivity as sea-water. In this case the resistance 

 of the tissue initially rises, very often from the initial sea-water value 

 of 1100 ohms to 1750 ohms in the first fifteen minutes. The resistance 



